Is Sourdough or Whole Wheat Bread Better for Your Gut? We Asked Nutritionists

When it comes to the wonderful world of bread, sourdough and whole wheat are both often touted as nutritious options. But if you're on a mission to prioritize gut health, you might wonder which of these two breads is better. Both varieties, after all, offer essential nutrients that benefit digestion (and beyond). We asked registered dietitians to explain how each type of bread affects the gut and whether one is superior to the other.

Sourdough Nutrition

Sourdough bread is made of flour, water, salt, and a mixture known as a "starter." The starter (which leavens the bread) consists of water and flour that's been fermented by wild yeast and lactic acid bacteria, says Diana Guevara, RD, registered dietitian and nutritionist supervisor with the Nourish Program at UTHealth Houston.

The fermentation process contributes to sourdough's iconic taste and texture. It's also responsible for several nutritional aspects:

• Supports healthy blood sugar: "The fermentation process produces organic acids, such as lactic and acetic acids, that can lower the glycemic load [of the bread]," says Jacob Howman, MS, RDN, LD, registered dietitian nutritionist at The Ohio State University Wexner Medical Center. This means it causes a smaller rise in blood sugar than other types of bread.
• Improves mineral absorption: Lactic acid bacteria, which ferment the starter, supports the absorption of minerals like iron, zinc, and magnesium, per Howman. That's because it breaks down phytic acid, a natural substance found in plant-based foods that blocks the absorption of certain minerals.
• Reduces digestive symptoms: "Fermentation [makes] the bread easier to digest and reduces FODMAPs, which aids in digestion for some people," says Jessica Zinn, MS, RD, CDN, CDCES, registered dietitian at Northwell's Lenox Hill Hospital. "FODMAPs" stands for fructose and galactooligosaccharides, disaccharides, monosaccharides, and sugar alcohols, which are types of carbs that can cause digestive symptoms in some people.

Sourdough is also rich in prebiotic fibers and resistant starch, says Zinn. Both nutrients feed the "good" bacteria in the gut. Additionally, if sourdough bread is made with whole wheat flour, it will provide B vitamins, iron, zinc, and magnesium, Guevara says.

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Whole Wheat Nutrition

Whole wheat bread is made with whole wheat flour, which includes the entire wheat kernel, per Zinn. This includes the fiber-rich outer layer called the bran. The flour is mixed with yeast, water, and salt to create the dough, according to Zinn.

Due to the use of the whole wheat kernel, this type of bread is rich in fiber, Zinn explains. This includes soluble fiber, which increases healthy gut bacteria and lowers cholesterol and blood sugar levels, and insoluble fiber, which improves bowel health, says Howman. What's more, "the fiber in whole wheat serves as fuel for gut microbes, which ferment it into short-chain fatty acids (SCFAs)," shares Howman. These SCFAs reduce inflammation and provide energy to intestinal cells, he says.

In addition to fiber, whole wheat has the "B vitamins thiamin, niacin, and folate, and the minerals iron, zinc, and magnesium," notes Guevara. It also contains phytochemicals, which are antioxidants linked to a lower risk of heart disease, type 2 diabetes, and many cancers, says Howman.

Which Is Better for Gut Health?

"If your goal is overall gut health and you don't have any GI conditions, both sourdough and whole wheat breads are excellent choices," says Howman.

It's worth noting that each bread supports the gut in different ways. Sourdough enhances mineral absorption, increases resistant starch, and potentially makes digestion easier. Whole wheat bread contains more fiber, a nutrient that supports regularity, feeds gut bacteria, and increases SCFA production, per Howman.

You can also go for sourdough made with whole wheat flour, which will give you the best of both worlds in a single bite. This way, you'll get the benefits of lactic acid fermentation as well as the fiber, vitamins, and minerals from the whole wheat flour, says Guevara.

If you have non-celiac gluten sensitivity or irritable bowel syndrome, sourdough might be the best choice, says Howman. The fermentation reduces gluten and breaks down FODMAPs—which, as mentioned, can trigger digestive symptoms in some people.